<template>
    <div class="s-canvas">
        <canvas id="s-canvas" :width="contentWidth" :height="contentHeight"></canvas>
    </div>
</template>
<script type="text/javascript" src="js/echarts.js"></script>
<script>
    export default{
        name: 'SIdentify',
        props: {
            identifyCode: { // 默认注册码
                type: String,
                default: '1234'
            },
            fontSizeMin: { // 字体最小值
                type: Number,
                default: 25
            },
            fontSizeMax: { // 字体最大值
                type: Number,
                default: 35
            },
            backgroundColorMin: { // 验证码图片背景色最小值
                type: Number,
                default: 200
            },
            backgroundColorMax: { // 验证码图片背景色最大值
                type: Number,
                default: 220
            },
            dotColorMin: { // 背景干扰点最小值
                type: Number,
                default: 60
            },
            dotColorMax: { // 背景干扰点最大值
                type: Number,
                default: 120
            },
            contentWidth: { // 容器宽度
                type: Number,
                default: 90
            },
            contentHeight: { // 容器高度
                type: Number,
                default: 38
            }
        },
        methods: {
            // 生成一个随机数
            randomNum (min, max) {
                return Math.floor(Math.random() * (max - min) + min)
            },

            // 生成一个随机的颜色
            randomColor (min, max) {
                let r = this.randomNum(min, max)
                let g = this.randomNum(min, max)
                let b = this.randomNum(min, max)
                return 'rgb(' + r + ',' + g + ',' + b + ')'
            },

            drawPic () {
                let canvas = document.getElementById('s-canvas')
                let ctx = canvas.getContext('2d')
                ctx.textBaseline = 'bottom'
                // 绘制背景
                ctx.fillStyle = '#e6ecfd'
                ctx.fillRect(0, 0, this.contentWidth, this.contentHeight)
                // 绘制文字
                for (let i = 0; i < this.identifyCode.length; i++) {
                    this.drawText(ctx, this.identifyCode[i], i)
                }
                this.drawLine(ctx)
                this.drawDot(ctx)
            },

            drawText (ctx, txt, i) {
                ctx.fillStyle = this.randomColor(50, 160) // 随机生成字体颜色
                ctx.font = this.randomNum(this.fontSizeMin, this.fontSizeMax) + 'px SimHei' // 随机生成字体大小
                let x = (i + 1) * (this.contentWidth / (this.identifyCode.length + 1))
                let y = this.randomNum(this.fontSizeMax, this.contentHeight - 5)
                var deg = this.randomNum(-30, 30)
                // 修改坐标原点和旋转角度
                ctx.translate(x, y)
                ctx.rotate(deg * Math.PI / 180)
                ctx.fillText(txt, 0, 0)
                // 恢复坐标原点和旋转角度
                ctx.rotate(-deg * Math.PI / 180)
                ctx.translate(-x, -y)
            },

            drawLine (ctx) {
                // 绘制干扰线
                for (let i = 0; i < 4; i++) {
                    ctx.strokeStyle = this.randomColor(100, 200)
                    ctx.beginPath()
                    ctx.moveTo(this.randomNum(0, this.contentWidth), this.randomNum(0, this.contentHeight))
                    ctx.lineTo(this.randomNum(0, this.contentWidth), this.randomNum(0, this.contentHeight))
                    ctx.stroke()
                }
            },

            drawDot (ctx) {
                // 绘制干扰点
                for (let i = 0; i < 30; i++) {
                    ctx.fillStyle = this.randomColor(0, 255)
                    ctx.beginPath()
                    ctx.arc(this.randomNum(0, this.contentWidth), this.randomNum(0, this.contentHeight), 1, 0, 2 * Math.PI)
                    ctx.fill()
                }
            }
        },
        watch: {
            identifyCode () {
                this.drawPic()
            }
        },
        mounted () {
            this.drawPic()
        }
    }
</script>